<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .hello{
            width: 100px;
            height: 100px;
            background: pink;

            /* display: none; */
            /* display: block; */
            display: inline;

            /* 行级元素不支持width和height */
        }
        .world{
            background: green;
            display: inline-block;

            width: 200px;
            height: 50px;
        }

        .btn{
            width: 180px;
            height: 40px;
            background: #4662d9;
            color: white;
            font-weight: bold;
            font-size: 16px;
            border: 0;
            border-radius: 8px;
        }
        .btn:hover{
            background: #1434c6;
        }

        .btn2{
            display: inline-block;
            width: 180px;
            height: 40px;
            background: #4662d9;
            color: white;
            font-weight: bold;
            font-size: 16px;
            border-radius: 8px;
            text-align: center;
            line-height: 40px;
        }
        .btn2:hover{
            background: #1434c6;
        }

    </style>
</head>
<body>
    <div class="hello">万和</div>aaa

    <span class="world">Java开发</span>bbb
    <hr>

    <input type="button" value="登录" class="btn"> 

    <span class="btn2">注册</span>
</body>
</html>